A tire air valve is mounted or installed into a tire for every vehicle, e. g., bicycles, motor cycles and automobiles including a commercial vehicle or truck, a motor bus and a passenger car. Such a valve commonly includes a casing in the form of a tubular or hollow cylindrical body that is a portion secured into a tire, and a valve "core" or body portion which when received in place in the tubular casing provides a conventional air valve mechanism and its pressure air inlet and closure functions.
To provide these functions and the air valve mechanism, the valve core is typically provided with an air inlet passage formed in a space between a tubular part with both ends open and a shaft passing through the tubular part coaxially therewith. The shaft has a flange secured thereto and is spring biased in the tubular part so that the flange normally closes one end (on the side proximal to the tire interior) air tight. The tubular part is associated with a head portion, called a "valve core head" portion, at the side distal to the tire interior, through which air is led from a pneumatic pump. The valve core shaft portion past the tubular part extends through and protrudes from the head portion and has a round and somewhat enlarged end face at its top or foremost end. When the shaft is pushed with a force applied onto that enlarged end surface, the shaft is moved against the spring bias relative to the tubular part that is fixed in position to the valve tubular casing to provide an opening between the closing flange and the tubular part, thereby establishing fluid communication of the air inlet passage with the tire or tire tube interior.
To ease assembling and disassembling the valve, the tubular valve casing is formed with a threaded inner surface and the valve core is provided with a threaded outer surface typically on the valve core head portion so that these two surfaces may be in mesh or interlocked with each other. Therefore, tire air valves for vehicle tires, regardless of types of the tyres in which they are loaded, commonly have a design such that screwing the valve core into the tubular casing may assemble the valve, i. e., make the valve core assume its operative position, and unscrewing the valve core from the tubular valve casing may disassemble the valve, i. e., may detach the valve core from the casing. With the valve assembled, the entire valve core including the head portion and the portion of the shaft that protrudes from the head portion must be accommodated within the tubular casing in order to protect it from any damaging external force.
Needs arise to disassemble or dismount and then to assemble or mount again a tire air valve of design as described. One situation that requires a tire air valve to be disassembled is, suffice to say, when its valve core is broken and needs to be replaced with a new valve core. Another situation imposing the requirement somewhat unique is when it is desired to inject a tire life extending (puncture preventive) liquid agent or component into a tire, conveniently through a tire air valve as mentioned above.
When a need arises to detach the valve core from the tubular casing in the tire in such a situation, use has so far been commonly made of a tool with a shaft or shank formed at its top with a slot or recess simply designed to allow the valve core head portion to be picked or pinched, requiring the user or operator to use both hands. It has been found that such conventional tools are not only inconvenient because of necessitating both hands in accomplishing an operation whereby a valve core is unscrewed from or screwed into its valve tubular casing. They have also been found to be unreliable even with considerable skill. From such a tool the valve core may very often come off and fall by gravity.
It must also be noted that especially for a commercial vehicle or a motor bus which employs a double type tire on each of its rear tyre wheel, its outer part tire has a tire air valve arranged to face inwards and yet to lie close to the tire wheel. As a result, the space open to the operator's operation in such a vehicle is quite limited and so narrow that even the operator's hands alone cannot be easily admitted, thus making the operator's two hand operation extremely difficult.
To make matters worse, tires for automobiles entail a specified air pressure that is considerably elevated. Thus, during a valve core detaching--mounting operation, air blows intensively from the tire air valve even for a moment, making it difficult even to keep the valve core retained on the tool. Rather, it has often be the case that a valve core comes to be blown off by the high pressure air blow from the valve, and eventually be lost. Such incidences are especially salient with tire air valves in the tires on automobiles such as commercial vehicles or motor buses in which the air pressure is even more increased.